Thermal sleeves

If the temperature of the superheated steam exceeds the saturation temperature by 28 to 30 °C (50-54 °F), a thermal sleeve is used to attach the nozzle to the steam line and reduce thermal stresses on the nozzle. Isokinetic sampling is especially important where the steam may contain suspended particles. 

The feedwater lines enter the containment via two lines, each with inner and outer isolation valves, splitting up into four lines adjacent to the RPV for connection to four nozzles, at "mid-height" of the vessel. The nozzles and the internal removable feedwater distributers are of a special ABB Atom design that ensures a "thermal sleeve" protection against the "cold" feedwater for the RPV wall, and efficient distribution into the downcomer. The feedwater flow rate is adjusted to match the steam flow rate from the vessel, to keep the water level within close limits, by speed control of the feedwater pumps at high power operation, but valve arrangements enable flow rate control also at low reactor power levels in these situations the feedwater flow is routed via smaller nozzles that can easier withstand thermal transients. 

PFR replacement reheater tube bundle, reheater thermal sleeve. 

Cracking of internal core spray piping has been observed at numerous BWRs [5.18]. Cracking has been found in the thermal sleeve collar, the downcomer slip joint sleeve (a creviced weld), and the downcomer piping elbow weld. Accessibility for inspection of creviced locations is extremely limited. 

Elbows at Boiling Water Reactors on February 6, 1997 [5.21] which notes that the riser elbow cracking observed at both BWRs occurred in the weld heat-affected zone of the riser elbow to thermal sleeve attachment weld appears to be characteristic of IGSCC. 

Thermal sleeves and nozzle safe ends connected to these components... 

Fig. 9.3. Sectional view of the Sequoyah pressurized water reactor (courtesy of Nuclear Engineering International). A, Control rod drive head adaptors B, instrumentation ports C, thermal sleeves D, upper support plate E, support column F, control rod drive shaft G, control rod guide tube H, internals support ledge J, inlet nozzle K, outlet nozzle L, upper core plate M, baffle and former N, fuel assemblies O, reactor vessel P, thermal shield Q, access port R, lower core plate S, core support T, diffuser plate U, lower support column V, radial supports W, instrumentation thimble guides.

Mechanical Design. Typically, each battery will have a thermal sleeve around each cell. The cells are mechanicily restrained by clamping them in a precision-machined sleeve. These sleeves can be made of either a metal such as aluminum or a composite made in a manner to provide electrical isolation, high thermal conductivity and strength. The sleeve is isolated electrically from the cell by a blanket, such as CHO-THERM which allows thermal transfer, wrapped around the cylindrical portion of the cell between the cell and sleeve. The space between the sleeves, blanket and cell is normally filled with a material such as an RTV 566 to provide better thermal transfer as well as to bond the interfaces mechanically. The sleeves are then either attached mechanically to a base plate which is the interface to the satellite structure or are attached to an interface such as extruded heat pipe assemblies which are a part of the satellite structure. The exposed surfaces of the cells are protected by a coating of Solithane or a combination of paint on the cell pressure vessel and Solithane. The desired battery voltage defines the number of cells used for the assembly. 

Hexagonal shaped lateral alignment/support plates on thermal sleeves are aligned... 

Hexagonal shaped Flow Guides aligned with lateral alignment/support plates on thermal sleeves and slip fit (attached later) into holes in Upper Support Plate... 

The RPV of a Super FR is illustrated in Fig. 3.5 [3]. The RPV of the Super LWR is similar to that of the Super FR. Like a typical RPV in PWRs, it has no major penetrations through the lower head. Control rods are inserted from the top of the core because there are no steam separators or dryers. All the internal walls are cooled by the inlet coolant. Only the outlet nozzles are exposed to the hot outlet coolant consequently, they may require a thermal sleeve. This limited exposure avoids thermal creep of the structural steel at the elevated temperature so the conventional steel of the PWR vessel can be used. There are only two inlet and outlet nozzles because the coolant or steam flow rate per electric power is smaller than that of LWRs. 

Effective thermal insulation of outlet nozzles through choice of a suitable thermal sleeve design... 

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